Just the facts

Sprains are a stretch and/or tear of a ligament, the tissue connecting two bones. Ligaments stabilize and support the body's joints. For example, ligaments in the knee connect the upper leg with the lower leg, enabling people to walk and run.

Strains are a twist, pull and/or tear of a muscle and/or tendon. Tendons are cords of tissue that connect muscles to bones.

Breaks are a fracture, splinter or complete break in bone, often caused by accidents, sports injuries or bone weakness.

Health care providers attend to millions of Americans with musculoskeletal injuries each year, according to the American Academy of Orthopaedic Surgeons (AAOS). More than one in four Americans has a musculoskeletal condition that needs medical attention.

Sprains

A sprain is caused by trauma -- a fall, twist or blow to the body, for example -- that knocks a joint out of position and overstretches or even ruptures supporting ligaments. Some examples: When you land on an outstretched arm, slide into a base, land on the side of the foot or run on an uneven surface.

Although the intensity varies, pain, bruising and inflammation are common to all three categories of sprains: mild, moderate and severe. You may feel a tear or pop in the joint. With a severe sprain, ligaments tear completely or separate from the bone. This loosening interferes with joint function. A moderate sprain partially tears the ligament, producing joint instability and some swelling. A ligament is stretched in a mild sprain, but there is no joint loosening or instability.

Sprains happen most often in the ankle, and are more likely if you've had a previous sprain there. Repeated sprains can lead to ankle arthritis, a loose ankle or tendon injury.

Strains

Acute strains are caused by stretching or pulling a muscle or tendon. Chronic strains are the result of overuse of muscles and tendons, through prolonged, repetitive movement. Inadequate rest during intense training can cause a strain.

Typical symptoms of strain include pain, muscle spasm, muscle weakness, swelling, inflammation and cramping. In severe strains, the muscle and/or tendon is partially or completely ruptured, leaving the person incapacitated. Some muscle function will be lost with a moderate strain, in which the muscle/tendon is overstretched and slightly torn. With a mild strain, the muscle/tendon is stretched or pulled, slightly.

These are some common strains:

Back strain. When the muscles that support the spine are twisted, pulled or torn. Athletes who engage in excessive jumping -- during basketball or volleyball, for example -- are vulnerable to this injury.

Hamstring muscle strain. A tear or stretch of a major muscle in the back of the thigh. The injury can sideline a person for up to six months. The likely cause is muscle strength imbalance between the hamstrings and the quadriceps, the muscles in the front of the thigh. Kicking a football, running or leaping to make a basket can pull a hamstring. Hamstring injuries tend to recur.

Breaks

Bone breaks, unlike sprains and strains, should always be looked at by a health care provider to ensure proper healing. Call your provider if the pain does not subside.

Athletes are most susceptible

All sports and exercises, even walking, carry a risk of sprains. The areas of the body most at risk for a sprain depend on the specific activities involved. For example, basketball, volleyball, soccer and other jumping sports share a risk for foot, leg and ankle sprains.

Soccer, football, hockey, boxing, wrestling and other contact sports put athletes at risk for strains. So do sports that feature quick starts, such as hurdling, long jump and running races. Gymnastics, tennis, rowing, golf and other sports that require extensive gripping put participants at higher risk for hand strains. Elbow strains frequently occur in racquet, throwing and contact sports.

Treating injuries

A severe sprain or strain may require surgery or immobilization, followed by physical therapy. Mild sprains and strains may require rehabilitation exercises and a change in activity during recovery.

In all but mild cases, your health care provider should evaluate the injury and establish a treatment and rehabilitation plan.